GEOTHERMAL ENERGY

Geothermal energy is the natural heat generated from within the earth. Undemeath the earth’s relatively thin crust, temperatures range from 1000 to 4000 C and in some areas, pressure exceeds 20,000 pounds per square inch (Psl).

Geothermal energy is most likely generated from radioactive thorium, pot assium and uranium dispersed evenly throughout the earth’s interior which produce heat as part of the decaying process. Volcances, hot springs, geysers and fumaroles are natural clues as to the presence of geothermal resources near the surface and perhaps where economic drilling operations can tap their heat and pressure. About 10 percent of the worlds land mass contains accessible geothermal resources and could provide several million quads of energy annually.

Geothermal energy is derived using the earth’s natural fluids to extract thermal energy that can be sent through turbines to generate electricity or be used directly e.g. direct heating and industrial process heat. Conventional oil and gas drilling methods are primarily used to extract ge0thermal resources using harder drill bills to combal corrosion and high temperature. As it is uneconomical to transport the thermal energy over long distances, the end use is often located near the source.

OCEAN THERMAL ENERGY CONSERVATION

OTEC utilizes the temperature different between warm (26 C) surface waters of low latitude tropical oceans and the cool deep waters (5-10 C) lying below a depth of a few hundred meters to run a turbine and a generator via a heat exchanger and a suitable medium (e.g. ammonia or low pressure steam).

OTEC is a method of using solar energy stored as a temperature difference in the oceans.The earth’s oceans absorb solar radiation the major part of which they store as thermal energy in the warm surface waters. On the other hand, cold water layers move slowly from polar regions towards the equator at depths of less than 100 m. Thus, a vertical temperature difference of up to 25 C exists throughout the year at many tropical locations According to the fundamental laws of thermodynamics, this temperature gradient can be exploited as an energy source.

The ocean thermal gradient does not vary significantly from day to night and hence can be regarded as a steady source of energy. It does have however, a seasonal variation which increases with the distance from the equator.The natural power potential of the thermal gradient energy is estimated to be as large as 10 W (10 TW). Obviously it is not technically feasible to extract all this energy.

A fair estimation would be approximately 10 W as against the world installed electrical generation capacity of the order of 10 W.In India activities in this area are coordinated by the OTEC Cell at Indian Institute of Technology, Madras. A feasibility study of setting up a 5 to 8 MW pilot R & D OTEC plant off the main Anandman Islands is ready and a proposal for a feasibility study for installation of a 100 MW OTEC plant off Madras is under consideration.

Wave Energy

Waves result from the inferaction of the wind with the surface of the sea and represent a transfer of energy from the wind to the sea, The amount transferred depends on the wind speed, the distance over which it interacts with the water, and the length of time for which it blows. The largest concentraction of potential wave energy is located between the 40 and 60 latitudes in both the northern and southern hemispheres.Wave power systems convert the motion of the waves into usable mechanical energy which in lum can be used to generate electricity. These systems can be floating or fixed to the seabed offshore, or may be constructed at the edge on a suitable shoreline.

Wave energy is being extensively researched in several industrial countries, particularly Japan, Norway, U.K. and U.S.A.In India the research and development activity for exploring wave energy started at the Ocean Engineering Centre, Indian Institute of Technology. Madras in 1982 Primary estimates indicate that the annual wave energy potential along the Indian coast is between 5 MW to 15 MW per meter.

Hence theoretical potential for a coast line of nearly 6000 KW works out to 60000 MW approximately. However, the realistic and economical potential is likely to be considerably less.Various wave energy systems are now being studied. Theoretical and experimental work is in progress on the optimisation of various system components. An oscillating water column device has been designed and tested at the IIT, Madras, in laboratory conditions. An experimental energy power plant of 150 MW capacity is going to be installed at Vizhinjam beach near Trivandrum in Kerala.

Tidal Energy

Energy can be extracted from tides by creating a reservoir or basin behind a barrage and then passing tidal waters through turbines in the barrage to generate electricity. Tidal energy is extremely site specific requires mean tidal differences greater than 4 metres and also favourable topographical conditions, such as estuaries or certain types of bays in order to bring down costs of dams etc.

Since India is surrounded by sea on three sides, its potential to hamess tidal energy has been recognised by the Government of India. Potential sites for tidal power development have already been located. The most attractive locations are the Gulf of Cambay and the Culf of Kachchh on the west coast where the maximum tidal range is 11 m and 8 m with average tidal range of 6.77 m and 5.23 m respectively. The Ganges Delta in the Sunderbans in West Bengal also has good locations for small scale tidal power development.

The maximum tidal range in Sunderbans is approximately 5 m with an average tidal range of 2.97 m. The identified economic tidal power potential in India is of the order of 8000-9000 MW with about 7000 MW in the Gulf of Cambay about 1200 MW in the Gulf of Kachchh and less than 100 MW in Sundarbans.

The Kachchh Tidal Power Project with an installed capacity of about 900 MW is estimated to cost about Rs. 1460/- crore generating lectricity at about 90 paise per unit. The techno-economic feasibility report is now being examined.

Energy Sources

The change which is threatening the existence of life is another factor forcing to consider alternate energy sources. However the energy sources to be adopted will have to meet the varying needs of different countries and at the same time enhance the security of each one against the energy crisis or energy shortage that have taken place in the past. The factors that need consideration for the search for new energy sources should include:

(i) The global energy situation and demand

(ii) The availability of fossil sources

(iii) The efficiency of the energy sources

(iv) The availability of renewable sources

(v) The options for nuclear fission and fusion.

Available Energy Sources
1. Petroleum
2. Natural Gas
3. Coal
4. Nuclear Fission
5. Nuclear Fusion
6. Introduction to Batteries
7. Solid State Batteries
8. Fuel Cells
9. Super capacitors
10. Photo-voltaic cells
11. Photo-electrochemical Cells
12. Hydrogen Production
13. Hydrogen Storage
14. Biochemical Energy Conversion Processes